Comparing CO2 and H2O exchange of wetlands (high water table) to crops/forests (low water table)

<p>Today, peatlands only cover slightly more than 3.5 % of Germanys territory. However, they play an important role concerning greenhouse gas emissions (CO₂, CH₄). We can avoid most of these emissions by proper management of the water table. This leads to a large potential net benefit for climate mitigation when re-establishing valuable long-term carbon sinks at the same time. Measurements in peatlands are challenging because they are often situated in remote locations, and it is difficult to install measurement towers on these statically unstable soils.</p><p>Two wetlands in Germany (grey willow in NE Germany; black alder in Eastern Brandenburg) are compared to the TU Dresden cluster of sites close to Dresden. The wetlands receive comparatively little precipitation, e.g. the grey willow site receives on average 580 mm/year (average from 1991 &#8211; 2020) but the water table is dominated by the nearby river Peene (fluctuating in dependence of the hydrological conditions in its estuary area). Similar complexity exists for the black alder site with regard to the managed water table of the river Spree. Measurements are available from eddy-covariance since 2010 for the grey willow, and from 2010 to 2015 for the black alder.</p><p>Yearly, seasonal and daily data of CO₂ (gross primary production, ecosystem respiration) and H₂O are analysed relative to the water table and the climate forcing (radiation, vapour pressure deficit and wind). Special attention will be paid to the flux patterns at each site (fingerprints of ET, F_C and of WUE). A comparison to the long-term cluster sites (forests, grassland and crop rotation) allows a first assessment of the potential benefit of various land management systems for climate mitigation. However, uncertainty might be large due to the differences in soil and climate, as well as by the typical non-linearity of complex systems like the wetlands and their dependence to the water table.</p>